Helium escape valves are present in some dive watches for removing helium that has penetrated the watch case during saturation dives where divers inhale a gas mixture containing helium and oxygen. This allows them to stay inside a diving bell or underwater habitat for several days. During this time period, helium may penetrate the watch. In the absence of such a valve, the excess internal pressure caused by helium that has seeped in may, during the decompression phase, cause damage to the watch, such as, for example, loss of the crystal which may pop out or break.
Helium escape valves can be manual or automatic. Manual valves operate simply by tightening a sealing element, such as a head, onto the case middle, in the same way as a screw-in crown. Manual valves have the drawback that the watch is not water-resistant if the valve is not tightened up again after use. Automatic valves are activated automatically, as their name indicates, when the difference in pressure between the inside of the watch case and the external environment reaches a critical threshold. A first type of automatic valve is one that the user cannot block, the principles of which are described in Swiss Patent No CH491246. This valve, which, in most cases, is mounted flush with the case middle takes the form of a simple valve limiting the pressure inside the watch case. The drawback of this type of valve is that it opens automatically with no possibility of stopping gas escaping and therefore of fluid entering the watch, which is problematic when decompression is performed in a humid environment. To overcome this drawback, there is a second type of automatic valve which can be operated by the user by screwing/unscrewing the head, which causes an axial displacement of the latter, as described in European Patent No EP0554797. This second type of valve could be incorporated in a push button as disclosed in European Patent No EP2685327.
The valve of EP0554797 includes a hollow head provided with a skirt and a central core extended by a shaft. The head can be screwed onto a tube attached to the case middle forming part of the timepiece case. The tube includes a bottom through which the shaft passes with clearance. The core and the shaft are surrounded by a helical return spring. The spring is supported under the head via its first end. The second end of the spring is supported on a ring which in turn compresses a first sealing gasket disposed on the bottom of the tube. A second sealing gasket is arranged under the head opposite the tube. When the head is screwed onto the threaded portion of the tube, the second sealing gasket is pressed against the tube. Thereafter, the valve is inoperative and completely sealed via the second gasket and the effect of the spring on the first gasket. When the head is unscrewed, the second gasket under the head is no longer active and the gasket at the bottom of the tube is able to rise up against the return force of the spring when the pressure within the case becomes higher than the pressure outside. Gas is then evacuated from the interior of the watch to the exterior.
This second type of valve has the drawback that the head is mounted on the tube via a screw thread. Given that, throughout its life, the head is mainly in the rest position, i.e. the screwed-in position, there is a risk that the user will no longer be able to loosen it when the time comes. Further, excessive tightening of the head onto the tube risks, over time, damaging the second gasket positioned under the head. Conversely, insufficient tightening of the head risks keeping it in the open position.